A solution of urea (mol. Mass `60 g mol^(-1)`) boils of `100.18^(@)C` at one one atmospheric pressure. If `k_(f)` and `K_(b)` for water are `1.86` and `0.512 K kg mol^(-1)` respectively, the above solution will freeze at:

Options

A. `-6.54^(@)C`
B. `6.54^(@)C`
C. `-0.654^(@)C`
D. `0.654^(@)C`

Answer

C

Explanation

`(DeltaT_(b))/(DeltaT_(f))=(K_(b))/(K_(f))`
`:.DeltaT_(f)=(K_(f))/(K_(b))xxDeltaT_(b)=(1.86)/(0.512)xx0.18=0.654`
`:. f.pt.=0-0.654=-0.654^(@)C`